Society has a growing concern to rapidly develop law enforcement leads in civil, criminal and terrorist acts in order to prevent subsequent acts. It is generally recognized that some form of broad surveillance methodology could help forensic investigators reconstruct the movement patterns of the subjects prior to arrival at the scene to be investigated. Reconstruction of such movements helps investigators to identify workshops, other supporting facilities, or modes and routes of transportation used by the subjects. These problems of rapidly uncovering such sites are made all the more pressing with concerns about terrorism.
Forensic investigative planners must make decisions regarding geographic areas to be targeted by surveillance methods. When significant knowledge of the subjects' movement patterns is already known, highly localized conventional surveillance methods can be continuously deployed to a few transit points. Absent detailed foreknowledge of the subjects' movement patterns, many more transit points must be monitored. In some cases, the investigators have no localizing information and might be forced to consider an entire community along with its transport network to be potential targets for surveillance. It is for such extreme situations that ubiquitous surveillance may be considered useful. If implemented with street level cameras, hundreds or thousands of cameras might be considered. However, civil liberty concerns and the high cost of supporting complete area surveillance preclude such systems from most areas. Continuous wide area aerial surveillance from circling manned or unmanned aircraft has been proposed as an alternative. However, the ability of aerial cameras to reliably trace vehicular movements can be questioned and the ability to trace pedestrians may be extremely problematic.
Particulate taggant technologies, ranging in size from atomic to macroscopic, are rapidly evolving as covert and overt means of verification of manufactured identification product and a broad range of other items. A particulate taggant can be understood to be any reliably recognizable small object that can be dispersed within or applied onto a large object without changing the general behavior of the large object. The physical basis of the reliable recognition of the small object can be variously based on, by way of example, distinctive compositions, color, or codes and evaluated through a variety of techniques including, but not limited to spectroscopy and microscopy. Heretofore, particulate taggants were affixed to products and items at the time of manufacture or storage by directly admixing the particles in bulk materials, such as explosive powder taggants, liquid product taggants, coating taggants to be applied as a finish to manufactured products, or directly affixed to products and items by adhesives, fasteners and the like.
Frequently arising during forensic investigations is the problem of determination of the route used by the subjects to reach the scene of forensic interest. Thus, there exists a need for a method by which particulate taggants are used forensically to understand movement patterns of a subject leading up to an incident of interest.
In the field of wide-area surveillance there exists a need for a method based on the dispersal and passive transport of particulate taggants throughout an area of interest.